title: Fatigue resistance and retentive force of cast clasps treated by shot peening.
abstract: OBJECTIVE
  The fatigue failure of denture clasps has often been observed in removable partial denture rehabilitation. To increase their fatigue strength, shot peening was evaluated as a surface treatment. In this study, we evaluated the fatigue resistance and retention of cast clasps by using a shot peening treatment.
  
  
  METHODS
  A cobalt-chromium (Co-Cr) alloy, commercial pure titanium (CP Ti), silver-palladium-gold (Ag-Pd-Au), and a gold-platinum (Au-Pt) alloy were cast and then treated with shot peening. The retentive forces of the clasps were measured up to a repetition of 10,000insertion/removal cycles in distilled water at 37°C. A fatigue test was also performed using a 15-mm cantilever. Specimens were loaded with a constant deflection of 2.0mm with 20Hz. A shot peening treatment indicated a better stability of retentive forces than that without shot peening. The retentive force of Co-Cr clasps without shot peening was remarkably decreased at 500 cycles of insertion/removal repetition.
  
  
  RESULTS
  The clasps with a shot peening treatment provided approximately 1.4-3.6 times higher fatigue strengths than those without a shot peening treatment.
  
  
  CONCLUSIONS
  To prevent the fatigue failure of the denture clasps and use the dentures for long term, a shot peening treatment would be recommended.
authors.affiliation: Department of Removable Prosthodontics, Tsurumi University School of Dental Medicine, Japan. tokue-ai@tsurumi-u.ac.jp
authors.forename: Ai
authors.initials: A
authors.lastname: Tokue
authors.forename: Tohru
authors.initials: T
authors.lastname: Hayakawa
authors.forename: Chikahiro
authors.initials: C
authors.lastname: Ohkubo
mesh_terms: D003722:Dental Alloys; D003735:Dental Casting Technique; D016734:Dental Clasps; D003775:Dental Polishing / Q000379:methods*; D003799:Dental Stress Analysis; D003781:Denture Retention; D003832:Denture, Partial, Removable; D008422:Materials Testing; D013314:Stress, Mechanical; D013499:Surface Properties
chemical_list: D003722:Dental Alloys
keywords: Clasp; Fatigue strength; Shot peening; Surface modification; Titanium